diff --git a/tools/preprocess_pragmas.c b/tools/preprocess_pragmas.c
index e31b863d07..5e750aab02 100644
--- a/tools/preprocess_pragmas.c
+++ b/tools/preprocess_pragmas.c
@@ -24,9 +24,14 @@ int main(int argc, char** argv) {
         return EXIT_FAILURE;
     }
     char* const version = argv[1];
-    const int len_version = strlen(version);
     char* const filename = argv[2];
 
+    const size_t len_version = strlen(version);
+    char version_needle[len_version + 2];
+    memcpy(version_needle, version, len_version);
+    version_needle[len_version] = ':';
+    version_needle[len_version + 1] = '\0';
+
     char buf[32 * 1024];
     char* const bufend = buf + sizeof(buf);
     char* bufp = buf;
@@ -90,13 +95,8 @@ int main(int argc, char** argv) {
             }
             if (is_in_pragma) {
                 *line_end = '\0';
-                char* version_amount_item = strstr(line, version);
+                char* version_amount_item = strstr(line, version_needle);
                 if (version_amount_item != NULL) {
-                    if (version_amount_item[len_version] != ':') {
-                        fprintf(stderr, "Found version %s in pragma line but no :amount attached\n", version);
-                        fprintf(stderr, "%s\n", line);
-                        return EXIT_FAILURE;
-                    }
                     char* version_amount_str_start = &version_amount_item[len_version + 1];
                     char* version_amount_str_end;
                     long amount = strtol(version_amount_str_start, &version_amount_str_end, 10);
diff --git a/tools/tests/README b/tools/tests/README
new file mode 100644
index 0000000000..843622e417
--- /dev/null
+++ b/tools/tests/README
@@ -0,0 +1 @@
+This folder contains tests for the tools living in this repo.
diff --git a/tools/tests/test_preprocess_pragmas.py b/tools/tests/test_preprocess_pragmas.py
new file mode 100644
index 0000000000..16caf3fd62
--- /dev/null
+++ b/tools/tests/test_preprocess_pragmas.py
@@ -0,0 +1,107 @@
+import difflib
+from pathlib import Path
+import subprocess
+
+
+# change to True to print output source on failed tests
+PRINT_FAILED_OUTPUT = False
+
+PREPROCESS_PRAGMAS_P = Path("tools/preprocess_pragmas")
+
+
+def fake_struct(pragma_line, i):
+    return f"struct increment_block_number_{pragma_line:05}_{i:03};"
+
+
+def fake_structs(pragma_line, amount):
+    return "\n".join(fake_struct(pragma_line, i) for i in range(amount))
+
+
+data = {
+    "test_noarg": (
+        "gc-us",
+        "source.c",
+        """\
+abc
+#pragma increment_block_number
+def
+""",
+        f"""\
+abc
+{fake_structs(2, 256)}
+#line 3 "source.c"
+def
+""",
+    ),
+    "test_one_arg_match": (
+        "gc-us",
+        "source.c",
+        """\
+abc
+#pragma increment_block_number "gc-us:17"
+def
+""",
+        f"""\
+abc
+{fake_structs(2, 17)}
+#line 3 "source.c"
+def
+""",
+    ),
+    "test_one_arg_no_match": (
+        "gc-us",
+        "source.c",
+        """\
+abc
+#pragma increment_block_number "gc-us-mq:17"
+def
+""",
+        f"""\
+abc
+{fake_structs(2, 256)}
+#line 3 "source.c"
+def
+""",
+    ),
+    "test_several_args": (
+        "gc-us",
+        "source.c",
+        """\
+abc
+#pragma increment_block_number "gc-us-mq:200 gc-us:250"
+def
+""",
+        f"""\
+abc
+{fake_structs(2, 250)}
+#line 3 "source.c"
+def
+""",
+    ),
+}
+
+for test_name, (version, filename, source_in, expected_source_out) in data.items():
+    p = subprocess.Popen(
+        [str(PREPROCESS_PRAGMAS_P), version, filename],
+        stdin=subprocess.PIPE,
+        stdout=subprocess.PIPE,
+        encoding="UTF-8",
+    )
+    source_out, _ = p.communicate(input=source_in)
+    if p.returncode != 0:
+        print(f"{PREPROCESS_PRAGMAS_P} ended with {p.returncode} on {test_name}")
+        exit(1)
+    if source_out != expected_source_out:
+        print(f"failed test {test_name}")
+        if PRINT_FAILED_OUTPUT:
+            print(source_out)
+        for l in difflib.unified_diff(
+            expected_source_out.splitlines(),
+            source_out.splitlines(),
+            "expected output",
+            "actual output",
+        ):
+            print(l)
+        exit(1)
+
+print("all tests ok")